PROMYCETES 

 Order 15. PUCCINI ALES 



Parasites; apothecia reduced to a mass of asci with the ascus-wall fused with 

 the spore-wall, i. e., teliospores with one or more cells; conidia normally present, 

 produced in aecia (aecidia), uredia, or pycnia (spermagonia), all of which are 

 frequently developed; the telia and the conidia forms may occur upon the same 

 host or upon diflferent hosts, any two or more may be associated, or any stage 

 except the pycnia may exist alone; the aecia normally possess a peridium, uredia 

 and telia only rarely, though paraphyses not infrequently occur; teliospores typi- 

 cally with 1 or more germination pores in each cell, giving rise to a promycehum 

 with sporidioles; promycelium exserted and filamentous, merely proliferated, or 

 entirely internal. 



The conidial stages of rusts lend strong support to the ecological view that 

 the telium is a reduced apothecium, probably to be derived from that of the 

 Agyriales. Chiefly as the result of an assured water-supply, the apothecium has 

 become reduced to a mass of asci and spores, in which the fusion of the two walls 

 has provided the necessary protection at maturity. The intense parasitism of the 

 group has rendered possible a new and very active evolution that has dealt espe- 

 cially with the number and association of the four spore-forms (cf. Arthur 1906). 



Two families are recognized in accordance with the treatment of Dietel (Nat. 

 Pflanzenf. 6:35 1928), but there is no clear dividing line between them. The 

 Pucciniaceae are regarded as ancestral and the Melampsoraceae as derived from 

 them by more or less reduction. 



Key to Families 



A. Teliospores typically single and stipitate, some- 



times united in a gelatinous mass or a definite 



body, or more or less fused in series Pucciniaceae p. 147 



B. Teliospores sessile, combined in flat crusts, pul- 



vinate masses, or columnar forms, occasionally 

 arising within the epidermal cells or in the 

 mesophyll Melampsoraceae p. 153 



Family 63. PUCCINIACEAE 

 Dietel 48; 7:528 



Teliospores typically stipitate, rarely sessile, seriate and somewhat united 

 laterally, 1-x-celled, promycelium exserted, proliferate, or internal; aecia mostly 

 with a peridium, but this occasionally rudimentary or lacking, or replaced by 

 paraphyses; uredia rarely with a peridium, sometimes with paraphyses, urediospores 

 separate, not catenate. 



When missing spore-forms are not indicated in the key, all four stages are 

 found. The geographical distribution and host-plants are likewise given for such 

 genera as are more or less restricted in either respect. 



147 



